1. Physics Department, Hokkaido University of Education, Sapporo 002
2. Faculty of Science, Tokyo Metropolotan University, Minami-Osawa 1-1, Hachioji, Tokyo 192-03
3. Department of Metal Physics, Charles University, Ke Karlovu 5, 12116 Prague 2, Czech Republic
4. Faculty of Science, Osaka University, Toyonaka, Osaka 560